Method of producing gem materials



stituent from solution or combination,-

Patented July 26, 1921.

LEON H. BARNETT, OF NEW YORK, N;

METHOD OF PRODUCING GEM MATERIALS.

No Drawing.

My invention relates to a method of producing extremely high pressure for the purpose of changing the character of certaln chemical elements, compounds or combinations, for instance, for converting carbon in the form of dissolved or combined carbon, or graphite into the allotropic form of diamond, or corundum into ruby, sapphire, etc. Broadly speaking the method comprises melting certain chemical elements or compounds, such as metals, alloys and nonmetallic substances, capable of expanslon under certain conditions of heatingor cooling; confining, as completely as possible, such substance or substances in a receptacle of great strength, such as a steel shell, and while thus confined, allowing the. mass to cool. The rate of cooling will be dependent upon the character of the contents and the method employed, further details of which will hereinafter appear, but in general, there should be an expansion of theinternal body during a primary cooling, or during heating following a secondary cooling.

Because of the resistance offered by the enclosing body to the expansion of the contents, which latter as a whole must have a different rate of expansion than the enclosing body, this expansion will be converted into internal pressure, and reacting upon the contents, composed of the original charge, and any material added, or any material which mighthave been formed during the process, will cause some or all of the contents to undergo changes in densitdy, allotropic form, hardness, strength an other qualities.

It is well known that certain alloys will expand upon solidifying, type metal be ng a well known example. Cast iron whlch can be considered as an alloy of iron and carbon will under certain conditions not shrink during the entire cooling process but will expand and remain expanded for a con siderable portion of time during the cooling In both cases the expansion is process.

a lighter concaused by the separation of thus causing it to occupy space which it did not previously occupy.

quenching the molten metal in water or pouring it into a metallic mold, or placing the mold into a molten metal such as lead or zinc, having a low fusion point, or air and But the cooling in the case of iron be rapld, such as Application med October 6, 1923. Serial No. 667,057.

cooling if the mass be small,then most of the carbon will remain combined with the iron, and there can be no expansion. But if such an ironbe thus cooled, and then slowly reheated, free carbon will form expansion occurring, and if confined-as a ove stated, pressure will be exerted upon the material'the form of which we desire to change. But there is still another case, and that is when there is no separation of metals or nonmetals, advantage being taken of the natural expansion of a metal or alloy or other substance under heat while confining it in a space, such as the interior of a shell, composed of a less fusible metal, and having a lower coefficient of expansion than the metal or alloy, or other substance containing the material the character of which is to be changed.

As the conditions favoring the expansion and contraction of ironare far more complicated than those of most of the other metals and alloys, and as iron may be the most important metal for the process, I shall explain my process more fully in connection with iron.

As stated above, cast iron will, under certain conditions, not shrink during the entire cooling process, but will expand for a considerable portion of time, during the cooling process. This phenomenon may be due to a variety of causes and I believe it to be due to the fact that the iron contains most of its carbon in graphite form, and also a substance such as phosphorus which retards solidification, thus permitting more time for the graphite to separate out, and also a substance such as silicon which will act as a precipitant of the carbon combined with the iron. The graphite separating'out needs additional space thus causing an expansion of the entire body of cooling metal. I pro-'- pose to melt such an iron, then to confine it so as to prevent expansion as much as possible, and theruto cool it slowly to give suflicient time for substantially all of the combined carbon to precipitate or separate out as graphite and thereafter to be held pntil the inaterial to be treated has been subjected to the desired pressure for the desired length of time to change its character as hereinabove referred to. The material to be treated may be either the dissolved carbon, the combined carbon or graphitic carbon which is present in the natural iron,

. the'hope of or graphite which has been added, or may be a material such as corundum which is added to the iron referably while the latter is in molten condition. Any material capable of withstanding the hi h heat of the molten iron and which may ave its character changed by subjection to high pressure may be treated by this method. Even the iron itself might have its character changed by this extensive pressure.

The length of time during which the material to be treated will have to be held subjected to pressure would have to be determined in each case by preliminary experiments. It is obvious that the pressure may be maintained for any desired period of time either by regulation of the rate of cooling the iron or by maintainin the iron at a temperature for the desire length of time at which optimum pressure is exerted.

Numerous experiments have been made in the past with cooling molten cast iron in generating a high interior pressure atthe time of the solidification of the iron, with the result that very minute particles of carbon were converted into the allotropic form of diamond, but in these experiments the greater part of the carbon remained in the combined form although some probably precipitated out as graphite before the beginning of the solidification and could, therefore, not have caused an interior pressure as in my process, the pressure exerted on the graphite being due undoubtedly to the contraction of the rapidly cooling iron.

I prefer to use in my process an iron containing about l to 5 92) of carbon. If the total carbon be over 4.3% and the cooling not too rapid the excess separates out before solidification and causes no expansion. The excess may be useful however for establishing nuclei of graphite which assist in the further separation of graphite. As the total carbon is reduced below 4.3%, less graphite can be produced, and hence there will be less expansion. I prefer also to have the iron containa sufiicient proportion of a substance which -will aid in the precipitation or separation of graphite, such as silicon, boron, or aluminum. In the case of silicon I prefer to use it in the proportion of 3%4%, preferably S If too much silicon is used, the precipitation of graphite will be retarded. I prefer also to have the iron contain a substance which will retard solidification, for instance, phosphorus, in the proportion of 1%1 preferably 1 4%. It is, of course, obvious that the exact percentage of each of the in redienta may have to be modified to meet t e needs of any particular operation but such percentages can readily be ascertained by brief preliminary experiments. Too much phosphorus tends to retard the precipitation of graphite. However, an injurious excess of phosphorus might be neutralized if a suflicient proportion of silicon were used.

If the sole object of the o eration is to produce pressure, the iron need not be heated .Very much beyond the point at which it becomes thoroughly fluid. However, if it be desired to precipitate or separate some graphite before the pressure be s, the temperature should be raised to sue a point that the desired amount of graphite will separate out. The total carbon should, however, be correspondingly increased.

Instead of casting the iron into a shell and allowing it to cool slowly therein, the molten mass may be allowed to form its own shell by a preliminary forced or quick cooling to be followed by slow cooling. The mass must be suflicient, however, to make possible a slow-cooling of its interior, otherwise even air cooling will be too ra id.

As already explained, t e rate of coolin between the beginning of the expansion and the time when the iron has contracted to its original volume should be slow enough to permit the separation of most of the graphite, in order to exert the necessary pressure which its formation produces to convert the carbon, or corundum, or the material added, into the desired form. Just what this length of time'is to be would have to be determined by experiment in each case but in any event the time allowed should be sufiicient to allow for the separation of most of the graphite. As graphite separates out very much more rapidly at 1100 C. than it does at 900 C., and as the presenceof silicon, aluminum, etc. aids in the separation, the time can be greatly reduced by carrying on the process under these favorable conditions.- Of course, if diamonds of considerable size are the pur pose of'the process, then the time must be sufficient to allow for the enlargement of the small diamonds that form.

Example 1.

An iron containing 4 A;% of carbon, 3% of silicon and 1% of phosphorus and as little sulfur as possible is heated until it is thoroughly molten. The molten metal is poured into a steel shell of great strength into which articles of opaque corundum had been previously introduced, and the aperture in the shell is then closed either by a plug or screwcap or by permitting the molten iron the aperture to sodidify and to form a lug. Before pouring, the steel shell should ave been heated to a red heat. The material is then permitted to cool to about 1050 C. and is kept at this temperature for one hour. At the end of this period it is allowed to cool to room temperature. The hardened material is cracked open or dissolved in acid so as to free the resulting rubies, sa phires, etc. from-the surrounding metal. S ome small diamonds should also be produced. The

color of the o aque corundum will determine the variety precious corundum produced.

A similar high pressure, with its accompanying action on carbon (and corundum if present), can be produced by rapidly cooling a mass of molten cast iron to tem eratures below 7 00 C. with consequent pro notion of cast iron in which most of its carbon is in the combined form. The cast iron will thereby be in a denser form, there having been no expansion during solidification and cooling. Now slowl raise the temperature to about 700800 and keep at this temperature until most of the carbon is in the free state; then cool and break shell or dissolve as before to isolate the gem material produced.

E example 2.

Use an iron of the same composition as in the previous example, and pour slowl into a cold shell into which had previously been placed some diamond dust. These minute particles of diamond will act as nuclei around which the free carbon will crystallize as it comes out from solution or combination with the iron. The pouring must be so slow that most of the carbon will remain in solution or combination. When the shell is entirely filled, including the opening, slowly raise the temperature to 750 'C and maintain it at this point for five hours. Then slowly cool, break open or dissolve the mass, and separate the diamonds.-

In case of an alloy such as type metal, fill the shell with the molten matter, in which is the material the character of which is to be changed. The opening can be closed as stated before by a plug or screw-cap, or the opening can be filled with molten iron and allowed to solidify. The mass can then be cooled either quickly or slowly, depending upon the purpose of the work, but in either case there will be expansion using type metal. In cases when expansion can occur with quick cooling as in this case, the metal can form its own shell by quenching or other rapid cooling. But such methods of rapid cooling should not be employed if sufficient time must be allowed for the material to crystallize out to commercial size.

In the process of utilizing the natural exansion of any substance during heating, be it a metal or alloy or even such substances as sulfur, hard rubber, tar, etc., a shell is filled with the melted substance, or substances, having a greater coefiicient of expansion than the shell, such as lead, or lead and carbon, or tar, and cooled. When cold, sufiicient material should be added to entirely fill the shell. Close shell as before and raise temperature. The material, the form of which is to be changed, could be added before casting, could be placed in the shell before pouring, or could be inserted later through an aperture drilled into the solid material, the drill-hold being then filled up and the heating then applied. When the material has reached a temperature that gives favorable results, this temperature should be maintained for the length of time suitable for the given material which is being treated. Of course, when the contents are fusible at comparatively low temperatures as lead and zinc, the contents could, at the end of the process, be melted, and poured out, without damaging the shell, and the materials then separated by any convenient method.

In cases where temperatures must be held at high points for a long time, it might be necessary to employ a special shell, for instance a three-ply shell; the inner layer of steel or wrought iron, covered with a layer of material which is an extremely poor conductor of heat, as lime or magnesia, and the third layer of cast iron, which might be formed by inserting the shell into a crucible or pot of cast iron, and then cooling.

In every case mentioned, we have a substance or substances capable of expanding under certain conditions of heating and cooling, such substance or substances being surrounded by a resistant shell, or crust, which it should fill as completely as possible at the beginning of the process, or at the time of greatest density, and which shell is capable of resisting as far as possible any expansion produced during the process. The result is extremely high internal pressure, with allotropic and other changes in certain chemical elements and compounds resulting in the production of sapphires, rubies, diamonds, bort, and other gem or gem-like materials.

I claim:

1. The improvement in the method of producing gem materials by high pressure which comprises melting an iron having a composition which would cause it to expand during cooling providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a rigid shell not of appreciably greater capacity than that occupied by such iron just previous to solidification and then slowly cooling such iron, substantially as and for the purpose described.

2. The improvement in the method of producing gem materials by high pressure which comprises melting an iron having a composition which would cause it to expand during cooling providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a space not appreciably greater than that occupied. by such iron just previous to solidification, slowly cooling such iron to a temperature at which the desired pressure is being exerted thereby, maintaining the iron at such temperatiire until the character of the material to be treated has been changed, and then completing the cooling of the iron, substantially as and for the purpose described.

3. The improvement in the method of producing gem materials by high pressure which comprises melting an ironhaving a composition which would cause it to expand during cooling and including a substance which aids in the precipitation of carbon therefrom, providing for the presence Within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a space not appreciably greater than that occupied by such iron just previous to solidification and then slowly cooling such iron, substantially as and for the purpose described.

4. The improvement in the method of producing gem materials by high pressure which comprises melting an iron having a composition which would cause it to expand during cooling and including a substance which tends to delay the solidification of iron during its cooling, providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a space not appreciably greater than that occupied by such iron just previous to solidification and then slowly cooling such iron, substantially as and for the purpose described.

5. The improvement in the method of producing gem materials by high pressure which comprises melting an iron having a composition which would cause it to expand during cooling and includin a substance which aids in the precipitation of carbon therefrom, and a substance which tends to delay the solidification of iron during its cooling, providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within 'a space not appreciably greater than that occupied by such iron just previous to solidification and then slowly cooling such iron, substantially as and for the purpose described.

6. The improvement in the method of producing gem materials by high pressure which comprises melting an iron having a composition which would cause it to expand during cooling and including silicon, providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a space not ied by cupied by such iron just previous to solidisubstantially as and for the purpose described.

8. The improvement in the method of producing gem materials by high pressure which comprises melting a substance, havfication and then slowly cooling such iron,

ing a composition which would cause it to' expand during cooling providing for the presence within the molten substance of a material which changes its character when subjected to high pressure, confining the molten substance within a rigid shell not of appreciably greater capacity than that occupied by such substance just prior to solidification and then slowly cooling such substance, substantially as and for the purpose described.

9. The improvement in the method of producing gem materials by high pressure, which comprises melting-aniron having a composition which will cause it to expand during cooling, and including a substance which aids in the precipitation of carbon under rapid cooling, providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, confining the molten iron within a space not appreciably greater than that occupied by such iron just previous to solidification, and then cooling such iron substantially as and for the purpose described.

10. The improvement in the method of producing gem materials by high pressure, which comprises melting an iron having a composition which would cause it to expand. during cooling, providing for the presence within the molten iron of a material which changes its character when subjected to high pressure, pouring such iron into a mold and allowing it to cool rapidly to below 700 (1, then raising the temperature to between 750 C. to 1100 C. and maintain that temperature until the character of the material to be treated has been changed substantially as and for the purpose described.

LEON H. BARNETT. 

